In a turbocharger which is used for vehicle engines, etc. such a configuration is adopted that exhaust gas from the engine fills a scroll formed in a turbine housing and passes through a plurality of nozzle vanes disposed on an inner peripheral side of the scroll to act on a turbine wheel disposed on an inner peripheral side of the plurality of nozzle vanes.
A plurality of nozzle vanes is disposed between two annular plates (a nozzle mount and a nozzle plate) such that a vane angle can be changed. These nozzle vanes, these two plates and a vane angle changing mechanism for changing vane angles of the nozzle vanes constitute a main part of the variable nozzle mechanism.
The variable nozzle mechanism is configured to change the angle of the nozzle vanes in accordance with the rotation speed of the engine, whereby the flow rate of the exhaust gas through an exhaust gas passage formed between those two plates and the rotation speed of the turbine wheel changes.
The main part of the variable nozzle mechanism is disposed between a turbine housing and a bearing housing which supports a rotation shaft of the turbine wheel. At the assembly, a gap is created between the variable nozzle mechanism (particularly, the nozzle plate) and the turbine wheel. This gap is sealed by mounting a seal ring therein.
As a conventional seal ring mounting method for a turbocharger and as a turbocharger with a seal ring, it has been known to mount a seal member of a disc spring type between a shroud having vanes for directing the exhaust gas to a turbine impeller and a turbine housing side section disposed facing the shroud (for instance, see Patent Document 1).
According to FIG. 1 of Patent Document 1, a shroud 010, as illustrated in FIG. 10 of the attached drawings, is configured by a plurality of vanes 09 for leading to a turbine impeller exhaust gas which is to be introduced to a scroll passage of a turbine housing 01, and two annular plates 09a, 09b which sandwich these vanes 09.
Further, in the turbine housing 01, a shroud opposing part 014 is formed opposite to the shroud 010 and an annular protrusion 027 is formed protruding toward the shroud 010 from an inner edge portion of an end face 014a of the shroud opposing part 014.
Between the shroud 010 and the shroud opposing part 014, a gap 015 is formed. A disc spring seal member 024 is disposed in this gap 015. Specifically, an inner peripheral end 025 of the disc spring seal member 024 is fitted to an outer peripheral surface of the annular protrusion 027 of the shroud opposing part 014 and contacts the end face 014a of the shroud opposing part 014 while an outer peripheral end 026 of the disc spring seal member 024 contacts the plate 09a of the shroud 010.